Animator exports include a lightweight JS for switching between scenes and timelines, and handling any interaction that you might have added to your animation. The JS controller triggers the animation by setting which scene should run at the beginning, so if you remove it, no scene will be run - this is why you animation appears not to be working after manually removing the controller.

If you only need CSS keyframe description, you can open the HTML file after export and locate @keyframes CSS line. To make it easier to spot, you can give the object in question (in your example the bouncing ball) an easy to identify ID under base-object->general->id.